(1) Technical Field
The present invention relates to recoverable energy absorbers, such as are used non-destructively and re-usably for absorbing energy in automotive and non-automotive applications.
(2) Background Art
Vehicle manufacturers spend considerable time and effort to eliminate BSR noises because they can be very irritating and annoying to vehicle drivers and passengers, particularly when the BSR noises come from a location close to a passenger's head, and/or any component in the vehicle's passenger compartment, especially when the noises are created near or are amplified by components that effectively form an echo chamber.
Many different geometrically shaped thermoformed energy absorbers are known, such as those described in U.S. Pat. Nos. 6,017,084; 6,221,292; 6,199,942; 6,247,745; 6,679,967; 6,682,128; 6,752,450; 7,360,822; 7,377,577; 7,384,095; and 7,404,593. These absorbers are said to provide dynamic reaction force characteristics that produce a relatively “square wave” shape when observing their reaction force properties as a function of deflection.
U.S. Pat. No. 8,465,087 describes a formed energy absorber with an integrated anti-squeak/anti-rattle feature which includes a protrusion (“countermeasure”) that suppresses or dampens buzzes, squeaks or rattles at the end wall of an energy absorbing structure. Such structures typically lie between a Class-A surface (such as a bumper fascia, a headliner, or a door trim panel) and a rigid sheet metal structure in automotive applications. The absorber is typically installed with a 3-5 mm gap from one surface and is attached to another. However, in some instances it becomes necessary to reduce the gap to improve the reaction response time at the primary area of impact prior to secondary impacts as for example the head rolls into adjacent structures. When the absorber contacts the opposing surface, an undesirable buzz or rattle can be heard. This noise occurs because a flat hard plastic surface can tap or vibrate against the opposing structure. The '087 patent describes an anti-buzz, squeak or rattle feature that is formed integrally with energy absorbers during the thermoforming process. However, this feature has proven difficult to form consistently, requires relatively a narrow processing window, and generally lacks the flexibility necessary to fully mitigate the translation of one structure to another that creates a BSR condition.
Materials such as foam, felt, and flock are often added to absorbers which lack an integrated structure to remedy the issue. A fabric pad, flock material, foam padding, or some other kind of flexible material if added to one of the surfaces responsible for making the noise may lessen or eliminate the severity of the buzzing or tapping or eliminate the possibility of one surface translating into the other. However, this solution requires the purchase and assembly of one or more separate components, and that results in added complexity, cost, and mass.